Pulsation reactor
The pulsation reactor technology is a thermal process for the production of finely divided powders with precisely defined properties. The special functional principle of the pulsation reactor technology leads to reaction parameters in a reaction environment that changes the properties in terms of surface, reactivity , homogeneity and particle size of the powder materials.
The technology has proven itself in particular for the production of nanoscale powders used for ceramic production as well as for the production of highly active catalysts . Simple oxides , but also particles such as zirconium (IV) oxide with doping elements or mixed oxides such as spinel , can be produced in the pulsation reactor.
history
A British scientist named B. Higgins discovered the appearance of the pulsating flame as early as 1777. In the specialist literature, this phenomenon was described as the “singing flame”. However, no suitable application was found until 1930. It was not until Paul Schmidt invented the ARGUS Schmidt tube (Figure 1) that pulsating combustion was used. The pulsating combustion was also used in the production of hot gas for heating purposes and in the steam boiler.
The principle was tested in the 1980s at the SKET Institute in Weimar with regard to the suitability of pulsating combustion as a unit for carrying out thermal, material-converting processes. Even at that time, the institute referred to the unit as a pulsation reactor. In addition to the process of burning cement clinker , the production of polishing agents from iron oxalate for the optical industry, as well as the production of surface-active catalyst carrier materials from Hydra (r) gillit, were investigated .
The pulsation reactor came to the fore from the 1990s through its use in environmental technology, especially for drying sewage sludge and for the regeneration of resin-bound foundry sands. From the year 2000 the pulsation reactor was then used for the production of catalytic powders on an industrial scale.
The principle of pulsating combustion (see Paul Schmidt ) has been further developed over the years by the current company IBU-tec advanced materials AG (emerged from the SKET Institute ), which finally tested and commissioned another test facility in 2008. By optimizing the reactors, it was now possible to use an oxidizing , inert or reducing hot gas atmosphere for material treatment. In addition, it was shown that the improved system was particularly suitable for the production of nanoparticles and catalytic powders.
Today the pulsation reactor is an established technology in chemical process engineering for the production of active particles with microstructural properties.
Structure and functionality
Basically, a pulsation reactor can be thought of as a periodically - unsteady working tube reactor that can be used for the thermal treatment of gas-borne substances.
Inside a hot gas generator on the reactor, the pulsating hot gas flow is generated by burning natural gas or hydrogen with ambient air. The hot gas flows through the so-called resonance tube, into which powder, liquid or gaseous starting material can be added. The treatment of the starting material is carried out by the hot gas flowing in the resonance tube and is terminated in a defined manner by suitable cooling. The finished product is deposited in a cleanable filter. During the entire ongoing process, the product can be removed with the help of a lock system and filled into barrels or big bags . An escape of the product into the environment can be completely excluded by a negative pressure prevailing in the reactor - including the filter.
In the resonance tube - the treatment room for the educt - the pulsing of the hot gas flow creates an almost piston-shaped flow with a temperature that is almost constant over the tube diameter. This piston-shaped flow leads to a narrow residence time distribution . In addition, the pulsating hot gas flow causes increased convective heat and material transport to and from the particles.
The hot gas can be generated in two different ways. Either the hot gas generator works with a high excess of air (λ ≥ 2), or the hot gas atmosphere can also be generated without oxygen or in a reducing manner. The range of hot gas temperatures in the pulsation reactor ranges from 250 ° C to 1,300 ° C. After adding the educt , it is possible that the actual treatment temperature deviates significantly from these values. The required treatment temperature can be determined through systematic experiments with temperature variation.
In addition to the treatment temperature and the type of hot gas atmosphere, there is also the option of pulsation, i.e. H. the spatially oscillating hot gas flow, without changing the system geometry in frequency and amplitude to match the material to be treated.
Process engineering peculiarities
The pulsating hot gas flow in the pulsation reactor enables very high heating rates and a greatly increased heat transfer from the hot gas to the particle in the thermal process. This is advantageous to target z. B. to be able to influence particle size, surface quality and phase composition.
With the pulsation reactor you are also not bound to the use of combustible starting materials . Non-combustible starting materials can also be used.
Due to the even temperature distribution in the reactor space and the narrow residence time distribution , the formation of hard aggregates is avoided and at the same time homogeneous material treatment is made possible.
The temperature range covered by the pulsation reactor is significantly higher than z. B. in spray dryers , whereby on the one hand gentle drying is only possible to a limited extent, on the other hand drying and calcination can be implemented simultaneously.
Properties of the pulsation reactor
The pulsation reactor has the following properties:
- Atomization of liquids, suspensions and solids (powder) as material feed
- short dwell time t: 100 ms - 10 s
- high heating and cooling rates
- Material treatment at temperatures from 250 ° C to 1,300 ° C
- Significant increase in heat and mass transfer from the resulting pressure and speed fluctuations of the pulsation (200% - 500%)
- homogeneous temperature distribution
- Selectable gas atmosphere: oxidizing , oxygen-free, reducing
Achievable material properties
- increased reactivity of the materials
- high specific surface area of the particles
- Avoidance of aggregate formation
- high material homogeneity (e.g. narrow particle size distribution)
- adjustable particle size from nano to micrometers
Typical fields of application
The materials produced in the pulsation reactor are used and processed in various branches of industry:
- Catalysts (automotive, industry)
- High-performance ceramics (bioceramics, optoceramics, protective ceramics)
- UV protection
- Effect pigments (paintwork, cosmetics, glass, ceramics, porcelain)
- Battery materials (coatings, electrode materials)
- Phosphors
- Additives (flame retardants, corrosion protection, thickeners)
- Fillers (volume increase, insulation effect).
Patents
- Patent application WO2007144060 A1 : Process for the production of garnet phosphors in a pulsation reactor. Registered on May 21, 2007, published on December 21, 2007, applicant: Merck Patent GmbH, inventors: Gerd Fischer, Tarek Khalil, Lars Leidolph, Holger Winkler.
- Patent application WO2002072471 A2 : Process for the production of multinary metal oxide powders in a pulsation reactor. Registered on March 6, 2002, published on September 19, 2002, applicant: Merck Patent GmbH, inventors: Stefan Remke, Bernd Mueller, Guenter Riedel, Stefan Ambrosius, Bernd Dahm.
- Patent application DE102006046803 A1 : Process and thermal reactor for the production of particles. Registered on September 29, 2006, published on April 3, 2008, applicant: Ibu-Tec GmbH & Co. KG, inventor: Stefan Ambrosius, Lars Leidolph.
- Patent application DE102006039462 B4 : Process for the production of particles. Registered on August 23, 2006, published on February 18, 2010, applicant: Ibu-Tec advanced materials AG, inventors: Gerd Fischer, Tarek Khalil, Lars Leidolph.
Web links
- The pulsation reactor
- Technical article: Periodically unsteady - The pulsation reactor, CIT_Plus, issue 5, pp. 34–36
- Technical article: Generation of a new generation of high-performance materials through pulsation reactor technology, Keramische Zeitschrift 65 (2013) [3] 170–173
- Technical article: The pulsation reactor - The innovation in thermal material treatment, NRC tradetrends, issue 4/14, p. 11
References
- S. Begand, B. Dahm, S. Ambrosius: Use of the pulsation reactor for substance treatment in the chemical industry. In: Chemical Engineer Technology. Volume 70, Issue 6, 1998, pp. 746-749.